What ca I do to fix the fuse for the door lock radio and internal lights it keeps burning 99 LHS?
If the fuse keeps poping (burning out) than you have a short that needs to be fixed. The fuses are there so if a wire does short (grounds out), the fuse will blow instead of the wiring heating up and melting or catching on fire. If the fuse pops as soon as you turn the key on, what you need to do is have plenty of fuses, best thing to do is disconnect one item at a time -- ie unhook the wires going to the radio(unhook the wires straight from the fuse block, not at the back of the radio), put a fuse in and see if it pops, if it does than its not the radio, unhook the wires for the door locks(straight from the fuse block again), put a fuse in, see if it pops, etc. Once you find out which device is causing the problem than you might be able to trace the wiring down and find where it is burned or where its somehow been moved and is grounding out. If you cant find it by using a visual inspecting (eyeballing it), than you will need a test light to find the short, but that becomes a whole other answer for using a test light to find a short.